1. Technical Field
The present invention relates to a time correction circuit that corrects the time based on, for example, electromagnetic waves received from outside of the circuit, and an electronic apparatus having the time correction circuit.
2. Related Art
A radio-controlled timepiece equipped with this kind of time correction circuit is generally known to be equipped with a radio-controlled timepiece reception module having a CPU that reads time information based on an electric signal received, an oscillator that outputs a clock pulse of 32 kHz, a frequency divider circuit that frequency-divides the clock pulse to output a time-measurement pulse of 1 Hz, and a real time clock having a time-measurement counter that counts up each of the bits when a predetermined number of time-measurement pulses are inputted. As the time information read by the radio-controlled timepiece reception module is reflected on the time-measurement counter of the real time clock, the radio-controlled timepiece can automatically correct the time thereon to the correct time received from outside (see, for example, Japanese Laid-open Patent Application 2008-211352).
The radio-controlled timepiece reception module of related art is a synchronous circuit that is controlled by the CPU. As each of the circuit blocks in the synchronous circuit is driven by the clock signal, the radio-controlled timepiece reception module is driven by a global clock that is a reference clock signal for the entire circuit in order to synchronize the circuit blocks. On the other hand, when a CPU with a low processing power is used in order to reduce the cost of the radio-controlled timepiece reception module, the frequency of the global clock is increased to increase the operation speed of the CPU, whereby the amount of processing per unit time is increased.
However, the current consumption in each of the circuit blocks increases in proportion to an increase in the frequency of the clock signal, which causes a problem in that, when the frequency of the global clock is increased in order to increase the operation speed of the CPU, the power consumption in circuits other than the CPU also increases. Also, there is another problem in that the clock signal generates increased noise due to electromagnetic radiation when its frequency is increased.